P296 18.3 线程存在的问题和临界区

ch18/thread4.c

@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <pthread.h>
+#define NUM_THREAD 100
+
+void *thread_inc(void *arg);
+void *thread_des(void *arg);
+long long num = 0;
+
+int main(int argc, char *argv[])
+{
+    pthread_t thread_id[NUM_THREAD];
+    int i;
+
+    printf("sizeof long long: %d \n", sizeof(long long));
+    for (i = 0; i < NUM_THREAD; i++)
+    {
+        if (i % 2)
+            pthread_create(&(thread_id[i]), NULL, thread_inc, NULL);
+        else
+            pthread_create(&(thread_id[i]), NULL, thread_des, NULL);
+    }
+
+    for (i = 0; i < NUM_THREAD; i++)
+        pthread_join(thread_id[i], NULL);
+
+    printf("result: %lld \n", num);
+    return 0;
+}
+
+void *thread_inc(void *arg)
+{
+    int i;
+    for (i = 0; i < 50000000; i++)
+        num += 1;
+    return NULL;
+}
+void *thread_des(void *arg)
+{
+    int i;
+    for (i = 0; i < 50000000; i++)
+        num -= 1;
+    return NULL;
+}